[Bug target/81907] memset called when it does not need to be; -mtune=cortex-a9

[dongkyun.s at samsung dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81907

--- Comment #15 from dongkyun.s at samsung dot com ---
> There's nothing in the compiler that explicitly says: use memset for these cores and not for others.  The choice will be down to available instructions and their relative costs.

Agreed, but, I'm just wondering why it has diffrent behavior according by GCC
version with -Os. (It should be same result if the choice is made by their
instructions and costs)